Spatially Multiplexed Receiver for OBI-Free Optical Networks
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Solution Overview
Problem
In multipoint-to-point optical networks, Optical Beat Interference (OBI) occurs due to simultaneous operation of multiple optical sources at different wavelengths, leading to noise floor increases and potential service interruptions, which existing methods like wavelength sorting or active tuning are costly and limited in scalability.
Innovation Solution
Employing a single large-area photodiode with spatial multiplexing techniques, such as butt-coupling or focusing lenses, to separate the images of return signal mode fields, effectively minimizing OBI noise by over 100 dB without requiring multiple receivers or expensive wavelength control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple optical sources operate simultaneously at different wavelengths, then network service capability is improved, but Optical Beat Interference (OBI) occurs causing noise floor increase and service interruptions
Solution Approach 1:
The patent segments the optical signals in the spatial domain by using multiple photodiodes arranged in a specific geometry (e.g., vertices of a polygon) to receive optical signals from different spatial directions. Each photodiode captures signals from specific optical paths, thereby separating the mixed optical signals spatially and preventing OBI while allowing multiple wavelengths to coexist
Solution Approach 2:
The patent transitions from temporal multiplexing (TDMA) or frequency multiplexing to spatial multiplexing by arranging photodiodes in different spatial positions. This dimensional change allows simultaneous reception of multiple optical signals without OBI, as the spatial separation prevents optical heterodyning while maintaining wavelength diversity
2Object-affected harmful factors
If passive wavelength bin sorting is used to avoid OBI, then OBI is reduced, but transmitter yield is reduced and system complexity increases due to multiple sort sub-sets
Solution Approach 1:
Instead of sorting transmitters before reception (traditional approach), the patent inverts the approach by using spatially arranged photodiodes to receive and separate signals after they are transmitted. This eliminates the need for pre-sorting transmitters into wavelength bins, maintaining transmitter yield while avoiding OBI through spatial separation at the receiver
3Object-affected harmful factors
If active wavelength tuning is used to avoid OBI, then OBI is avoided, but system cost increases due to expensive TECs and control systems
Solution Approach 1:
The patent replaces the mechanical/thermal wavelength tuning system (TECs, temperature control mechanisms) with a passive spatial filtering system using geometrically arranged photodiodes. This substitution eliminates expensive active control components while achieving OBI avoidance through spatial separation, significantly reducing system cost and complexity
4Object-affected harmful factors
If one receiver is used per return path transmitter to avoid OBI, then OBI is completely avoided, but system cost becomes prohibitively expensive for large numbers of splits
Solution Approach 1:
The patent merges multiple reception functions into a single receiver module by using multiple photodiodes within one integrated receiver. This configuration provides OBI avoidance equivalent to multiple separate receivers while using only one receiver unit, making the system cost-effective for large numbers of splits (64, 128, or 256-way splits)
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for efficient OBI suppression in a cost-effective manner, enabling the use of a single receiver for multiple transmitters across various wavelengths, including those identical, while maintaining sufficient bandwidth for commercial applications.
Implementation Method 1
receiving a plurality of optical signals from a plurality of optical paths using a single optical receiver having a large-area photodiode
Implementation Method 2
spatial multiplexing techniques, such as butt-coupling or focusing lenses, to separate the images of return signal mode fields
Data Source
AI summary
Receiving a plurality of optical signals from a plurality of optical paths using a single optical receiver having a large-area photodiode having an active area that is optically coupled to the plurality of optical paths provides significant commercial advantages such as lower cost as well as reduced size and maintenance.